For a while I have been wondering about utilizing super cheap(compared to regular 6374) hoverboard hub motors for my mtb build. I made a experiment and ordered few to play with. In orginal setup they are wired in star, which yielded 11500 erpm and around 10kmh(according to huawei app) with 11s. Later on I resoldered windings to delta, which gave 17500 erpm as expected.
Since it gave quite low speed output I decided to rewind them for higher kv. Motors have 27 poles and 30 magnets in outer shell. Original windings had following logic: AaABbBCcC … .
First I removed the old windings and managed to snap away the hall sensors(super easy to do) but it was not big issue since I can run it on sensorless mode. For rewinding I used 1,2 mm winding wire from local shop and made 6,5 turns per one teeth. While constantly measuring for shorts between and inside the stator I finished it after few hours. Unfortunetly when I ran motor I saw really low speed ~3000 erpm and current around 30 amps. After fail I thought maybe I did some winding accidently backward or some other error but after triple cheking everything was fine. Now, when Im out of ideas I came here to ask for some good suggestions or ideas, where I might have made mistakes. I still see quite a lot of potential on those beefy motors
Wow that’s a huge current for a no load spin if that’s what you’re saying. I’d go to rcgroups.com and ask there. I can’t look at a winding to tell but over there a couple people do that can tell what’s up
But maybe try the winding w a really thin wire and just a turn or two and test then before going the whole hog
Interesting project here… If it’s as simple as picking up broken hover boards from ebay, and rewinding their motors… I just wonder if these could handle the stresses of 20+mph.
I also wounder, when rewound, how much current they could handle.
I’ll check if anyone here has done anything like this here before moving to rcgroups. I have read quite a bit from here and there but haven’t got answers to my questions
What you mean by turn or two? Like two turns with thin(how thin is thin in mms?) wire around few teeth? What would be the benefits of doing that? Testing the strength of magnetic field?
@evoheyax Well if you look at their mass and therefore heat dissipation then in theory they might handle quite a bit(still in testing phase). Even better, after you wind it to higher kv with thicker wire than original, you might get even more speed out of them before signs of heating starts to show. There is way too much torque available right now.
The point of a few turns is to test that your winding/terminating correctly.
The issue you have is a super low kv resulting in too much torque and not enough speed.
If you do say 2 turns, you should have a really high kv. My advice is to start with a few turns , measure the kv and figure out what your speed will be, and keep adding more turns until your at the right speed for you.
Then, calculate what gauge wire you can get away with, try it, and adjust if needed.
If u get some really thin magnet wire that’s easy to wind and put just a couple quick turns(wraps) on each tooth you could test the winding without doing it with hard to manipulate thick wire.the point being to make sure winding correctly. Then it shouldn’t take anything near 30 amps w no load.
Depending if u have the room the LRK winding is super failproof and u skip every other tooth. Or wind two teeth and the one between to see fit
As I mentioned in orginal post, I made 6,5 turns. Original motor had 13 turns, somehow I assumed it could double the speed By keep adding you mean unwind the previous wire and do it again? Is there minimum amount of copper that is needed to make enough magnetic field in stator? What you mean by dipping? Applying some adhesive to coils to fix them in place?
@Hummie You can imagine the pain of winding it with this wire. I even managed to mess up at some points so I had to start everything from beginning. This thing sure needs patience.
I never heard of LRK winding. Is it like partly winding the motor? Some example would be awesome.
The number of turns (wraps) around the tooth produce the torque and it’s independent of how thick it is so u can test with very easy to manipulate thin wire and test the kv and that it’s wound right before using a fat wire.
Adhesive for the windings is necessary with the vibrations on an esk8. A very thin epoxy that can take heat
@Hummie Good tip on the heat conducting epoxy! I’ll read a bit about LRK windings.
@evoheyax I hope I can get away with some regular epoxy for start. I just would like to see the concept of reusing those motors in this purpose To mount motors to trucks I removed original axle and drilled in lathe with 17mm drill bit. After that I drilled with 8 mm to get the wires to other side. Original grub screw is holding flat side of axle to stop it rotating. Whole setup looks nice and stealthy.
Indeed, the idea right now is to test it and how it works. I wont have patience to wind more than two motors anyway, so I’ll do it for myself I just like that I can order the same motor from local shop for decent price. So I don’t have to hold spares and enjoy riding even more.
But back to the original post. You both suspect the problem might be in the winding configuration? This sure looks like some coils are working against another ones.
Just for follow-up.
I did some tests with original windings in delta configuration and 12s. FOC mode yielded 19500 erpm while bldc pumped it up to 22500 erpm.
BLDC, by my calculations((erpm/pole count)x tire size) could yield theoretical top speed of 30 kmh(enough for me). I guess this could be manageble with dual drive. Initial 10kmh test with 70% efficiency was made with single drive and there might be some drop of performance happening.
I do hope that you might have luck with rewinding. I’ve only done rewinding on a DC for an RC, so I could make it go faster. I will do some more studying on this.
But one question I had was these motors can you over volt them? I have a motor on my bicycle a 48 volt 1000w and it will normally go 28 mph and I run it with 56 volt and it runs great at about 33 mph now.
Would that work on these motors, and would you just need to get a new controller or maybe use the old one…?
In the fact it is the easiest way to squeeze more power out of them by overvolting. It gives the same effect as your bicycle motor does. Delta mode which is easy to do also helped quite a bit (square root 3 - 70% more kv).
For me 12s is the limit, since I would prefer to stay with vescs. It has great diagnostic tool to see whats going on inside the escs and is easy to set up with remotes and stuff.
Biggest benefit of going higher kv by rewinding would be adding more strands to winding therefore increase maximum current output. There isn’t much room but I think 6 strand of 0,5 mm wire with 7-8 turns could be possible.
By keep adding you mean unwind the previous wire and do it again? Is there minimum amount of copper that is needed to make enough magnetic field in stator? What you mean by dipping? Applying some adhesive to coils to fix them in place?
I just like that I can order the same motor from local shop for decent price. So I don’t have to hold spares and enjoy riding even more.